What has made Candlestick patterns so popular is the fact that they take market psychology and display it in a picture. The Hammer formation personifies this. A stock opens and sellers come in. At some point, buying resumes and the stock is able not only regain the opening but also push higher and close at or near the high. I find this pattern most interesting after long runs up and down. After a long down move it can show reversal and at a new high can show continued strength.